Shutterless optically stabilized capnograph
First Claim
1. A device for detecting the concentration of a gaseous component of a substantially gaseous flow stream, comprising:
- (a) a source of infrared radiation;
(b) a pair of physically separate infrared detectors disposed on the same substrate so as to receive incident radiation from said infrared radiation source and to produce electrical signals representative of the received incident radiation;
(c) means for directing at least a portion of said substantially gaseous flow stream between said detectors and said infrared radiation source;
(d) attenuating means, disposed between only one of said detectors and said directing means, for attenuating the incident radiation impinging upon only said one detector; and
(e) means for processing said electrical signals representative of the received incident radiation so as to produce an optically stabilized signal substantially unaffected by changes in the ambient temperature of the environment in which said device operates.
12 Assignments
0 Petitions
Accused Products
Abstract
Methods and apparatus for constructing optically stabilized, shutterless infrared capnographs are disclosed. The capnographs of the present invention provide the absolute concentration of the constituents of the respiratory airstream of a patient, without the thermal drift problems normally associated with thermopile detectors, thereby providing a device with a high degree of accuracy. The present invention eliminates the need for a mechanical shutter to modulate the incident infrared beam and the need for a modulated source, thereby increasing the reliability and response time of the devices disclosed. Capnographs which are substantially unaffected by changes in the ambient temperature at which they operate are provided by connecting pairs of optically filtered thermopiles in series and processing the resulting differential pair.
92 Citations
47 Claims
-
1. A device for detecting the concentration of a gaseous component of a substantially gaseous flow stream, comprising:
-
(a) a source of infrared radiation; (b) a pair of physically separate infrared detectors disposed on the same substrate so as to receive incident radiation from said infrared radiation source and to produce electrical signals representative of the received incident radiation; (c) means for directing at least a portion of said substantially gaseous flow stream between said detectors and said infrared radiation source; (d) attenuating means, disposed between only one of said detectors and said directing means, for attenuating the incident radiation impinging upon only said one detector; and (e) means for processing said electrical signals representative of the received incident radiation so as to produce an optically stabilized signal substantially unaffected by changes in the ambient temperature of the environment in which said device operates. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 44)
-
-
12. A device for detecting the concentration of constituents of the respiratory airstream of a patient, comprising:
-
(a) a source of infrared radiation; (b) a pair of physically separate infrared detectors, disposed on the same substrate so as to receive incident radiation from said infrared radiation source and to produce electrical signals representative of the received incident radiation; (c) means for directing at least a portion of said respiratory airstream of said patient between said detectors and said infrared radiation source; (d) attenuating means, disposed between only one of said detectors and said directing means, for attenuating the incident radiation impinging upon only said one detector; and (e) means for processing said electrical signals representative of the received incident radiation so as to produce an optically stabilized signal substantially unaffected by changes in the ambient temperature of the environment in which said device operates. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 45)
-
-
23. A device for detecting the concentration of constituents of the respiratory airstream of a patient, comprising:
-
(a) a source of infrared radiation; (b) a pair of physically separate infrared detectors for each constituent whose concentration is to be determined, said detectors being disposed on the same substrate so as to receive incident radiation from aid infrared radiation source and to produce electrical signals representative of the received incident radiation; (c) means for directing at least a portion of said respiratory airstream of said patient between said detectors and said infrared radiation source; (d) attenuating means, disposed between only one of said detectors in each pair and said directing means, for attenuating the incident radiation impinging upon only said one detector in each pair; and (e) means for processing said electrical signals representative of the incident radiation received at each pair of detectors so as to produce optically stabilized signals substantially unaffected by changes in the ambient temperature of the environment in which said device operates. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 46)
-
-
33. A shutterless infrared capnograph for detecting the concentration of constituents of the respiratory airstream of a patient, comprising:
-
(a) a source of infrared radiation; (b) a pair of physically separate infrared detectors disposed on the same substrate so as to receive incident radiation from said infrared radiation source which has passed through said respiratory airstream and to produce electrical signals representative of the received incident radiation; (c) a pair of physically separate reference infrared detectors disposed on said substrate so as to receive incident radiation from said infrared radiation source which has passed through said respiratory airstream and to produce electrical signals representative of the received incident radiation; (d) means for directing at least a portion of said respiratory airstream of said patient between said detectors and said infrared radiation source; (e) attenuating means, disposed between only one of said detectors and said directing means and between only one of said reference detectors and said directing means, for attenuating the incident radiation impinging upon only said one detector and upon said one reference detector; (f) a first optical filter disposed between said pair of infrared detectors and said directing means for passing a narrow band of energy about a wavelength readily absorbed by a constituent of the respiratory airstream of which its concentration is to be determined; (g) a second optical filter disposed between said pair of reference infrared detectors and said directing means for passing a band of energy excluding said wavelength readily absorbed by a constituent of the respiratory airstream of which its concentration is to be determined; and (h) means for processing said electrical signals representative of the received incident radiation so as to produce an optically stabilized signal substantially unaffected by changes in the ambient temperature of the environment in which said device operates, said processing means comprising means for determining the difference between electrical signals produced by said pair of infrared detectors and the difference between electrical signals produced by said pair of reference infrared detectors, means for determining a ratio between said differences, and means for computing from said ratio the concentration of the constituent of the respiratory airstream whose concentration is to be determined. - View Dependent Claims (34, 35, 47)
-
-
36. A method of detecting the concentration of a gaseous component of a substantially gaseous flow stream, comprising the steps of:
-
transmitting a beam of infrared radiation through said substantially gaseous flow stream; attenuating a portion of said infrared radiation which has passed through said substantially gaseous flow stream; detecting the intensity of said infrared radiation using a first detector and generating a first signal; detecting the intensity of only said attenuated portion of said infrared radiation using a second detector, physically separate from said first detector and disposed on the same substrate as said first detector, and generating a second signal; computing the difference between said first signal and said second signal and generating a difference signal; and processing said difference signal to produce an optically stabilized signal representative of the concentration of said gaseous component, whereby temperature gradients between said first and second detectors are prevented such that said optically stabilized signal is substantially unaffected by changes in the ambient temperature of the environment. - View Dependent Claims (37, 38, 39)
-
-
40. A method of determining the concentration of a constituent of the respiratory airstream of a patient, comprising the steps of:
-
transmitting a beam of infrared radiation through said respiratory airstream; attenuating a portion of said infrared radiation which has passed through said respiratory airstream; filtering said infrared radiation and said attenuated infrared radiation through an optical filter which passes a narrow band of energy about a wavelength readily absorbed by said constituent of said respiratory airstream; detecting the intensity of said filtered infrared radiation suing a first detector and generating a first signal; detecting the intensity of only said filtered and attenuated infrared radiation using a second detector, physically separate from said first detector and disposed on the same substrate as said first detector, and generating a second signal; computing the difference between said fist signal and said second signal and generating a difference signal; and processing said difference signal to determine said concentration of said constituent of said respiratory airstream of said patient substantially independent of changes in the ambient temperature of the environment. - View Dependent Claims (41, 42)
-
-
43. A method of monitoring the respiratory condition of a patient, comprising the steps of:
-
transmitting a beam of infrared radiation through a respiratory airstream of said patient; attenuating a portion of said infrared radiation which has passed through said respiratory airstream; filtering said infrared radiation and said attenuated infrared radiation through an optical filter which passes a narrow band of energy about a wavelength readily absorbed by a constituent of said respiratory airstream indicative of the respiratory condition of the patient; detecting the intensity of said filtered infrared radiation using a first detector and generating a first signal; detecting the intensity of only said filtered and attenuated infrared radiation using a second detector, physically separate from said first detector and disposed on the same substrate as said first detector, and generating a second signal; computing the difference between said first signal and said second signal and generating a difference signal; processing said difference signal to determine a concentration of said constituent of said respiratory airstream of the patient substantially independent of changes in the ambient temperature of the environment; and monitoring the concentration of said constituent of said respiratory airstream of the patient as an indicator of the respiratory condition of the patient.
-
Specification